A255666 Number of length n+6 0..3 arrays with at most two downsteps in every n consecutive neighbor pairs.

16384, 65536, 256012, 803246, 2036844, 4542671, 9169016, 17232696, 30665992, 52227111, 85761364, 136522338, 211563872, 320215410, 474655320, 690599060, 988121664, 1392636938, 1936059024, 2658175636, 3608266324, 4847003609

Offset: 1

Author

R. H. Hardin, Mar 01 2015

Keywords

• nonn

Comments

Row 6 of A255660

Examples

			Some solutions for n=2
..1....2....0....0....1....2....1....0....0....2....3....3....2....2....2....3
..0....3....3....1....1....3....1....0....2....0....2....1....3....3....3....3
..3....3....2....1....0....2....0....3....3....2....2....1....0....1....1....0
..3....0....0....3....0....3....2....0....3....2....3....1....0....3....3....3
..1....2....0....0....2....1....2....3....1....1....1....2....2....1....0....2
..0....3....0....1....0....3....2....0....2....3....2....3....1....3....3....3
..2....2....0....1....2....1....1....1....3....2....1....1....0....1....3....0
..0....1....0....1....3....2....1....1....0....3....0....1....0....2....0....0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A255660

Formula

Empirical: a(n) = (1/39916800)*n^11 + (1/302400)*n^10 + (143/725760)*n^9 + (137/20160)*n^8 + (686191/1209600)*n^7 + (68821/4800)*n^6 + (118924709/725760)*n^5 + (37326349/60480)*n^4 + (9666601859/907200)*n^3 - (165778309/8400)*n^2 + (24588142/3465)*n - 6396 for n>4